Will there be any problem with the column if I run acetic acid dissolved in water? The query is with respect to the nonpolar and polar column.
Please note that for analysis on GC, your sample should be volatile. If it is not, you need to make it volatile. e.g. in case of fatty acid, you have to prepare its methyl esters by esterification/ trans-esterification reaction.
Thank You , Dr M R Rathod. But my concern is regarding volatile fatty acids.. acetic, propionic, Butyric and Valeric acids.
No problems. Run on DB5-MS/ HP5-MS or Rtx5-MS column. If derivatized to their FAMEs then better, if not then you might not see stuff with significant intensities. First inject one by one to assign as to what is what, and then do a mixture and then inject. FID should be fine. Avoid water! No water in GC!
Thanks,
Biswa
you can not use aqueous sample in Gas chromatography. Another question comes in my mind is, why are you using acetic acid in water for fatty acid analysis?
For fatty acid analysis, first you should make derivative of your fatty acids i.e. methyl or ethyl esters. Then you can only inject your sample in GC. You can use Petrolium spirit/ether/ hexane for analysis.
You can inject water solution for the analysis of volatile or short chain fatty acids on GC/MS, see attached link. This method uses a polar wax column on a Varian Saturn 2000 GC/MS system. I have the method up and running in our laboratory, the problem is our old ion trap mass spectrometer is not sensitive enough to perform the analyses we want to do.
http://www.sciencedirect.com/science/article/pii/S0039914015003148
I have analyzed volatile short chain fatty acids (C2 - C6) by GC/MS using a J&W 122-7332 DB-WAXETR column (30mx0.25mmx 0.25um film) using conditions similar to those described in J. Sep. Sci. 2012, 35, 1905-1913. The aqueous sample needs to be acidified to ~pH2 with a strong acid such as H2SO4 (which protonates the COOH) and saturated NaCl (increases partitioning of the SCFAs into an organic solvent by a salting out effect). Then extract with ether. I used MTBE spiked at a relevant conc. with 4-methyl valeric acid as internal standard. Other literature reports that ethyl acetate (EA) or methylene chloride (CH2Cl2) can also be used but I was detecting acetic acid as a trace impurity in 2 different lots of EA. MTBE worked well and is slightly less volatile that diethyl ether. I did not access (CH2Cl2) since it forms the bottom layer and therefore makes it more difficult to perform the extractions in a high throughput manner.
Thank You, Mr. Schmitt. But I tried the same extraction procedure for aqueous solution of acetic acid without using NaCl with ethyl acetate, toluene, hexane, TBAB, TEA, Chloroform, Dichloromethane. These all were a failure. Some solvents the extraction was very less but in some acetic acid was not at all extracted. That is the reason I asked whether a polar column can be used to avoid such extraction or derivatization step.
See attached link for the direct detection of SCFA in aqueous solution without extraction into an organic phase.
http://www.ncbi.nlm.nih.gov/pubmed/16206138
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